This invention relates to an installation tool for an externally threaded insert or stud which is locked to the workpiece by a serrated lock ring.
The inserts and studs which this tool was designed to install are the type shown in U.S. Pat. Nos. 3,630,252 for "Stud Fastener Assembly with Integral Lockring," 3,404,415 for "Method of Making Fastener with Snap On Captive Locking Ring," 3,259,162 for "Insert with Frictionally Interlocked Locking Ring," 3,259,161 for "Fastener with Captive Locking Ring" and the like. These inserts and studs are used to provide a strong and hard threaded receptacle for fasteners in soft material, for repairing a workpiece which has been bored incorrectly, and for providing a securely locked stud for fastening other components to a workpiece. The lock ring on the fasteners disclosed in these patents is an internally and externally serrated ring of hard material that meshes with a serrated bourrelet on the stud or insert and is driven into the peripheral edge of the hole in which the insert is threaded to torsionally lock the insert or stud to the workpiece. The external serrations torsionally lock the lock ring to the workpiece, and the internal serrations of the lock ring meshing with the serrations on the bourrelet on the stud/insert lock it to the lock ring.
At present there are two methods for installing these stud/inserts: manually, and with installation tools. They can be manually installed by threading the insert into the threaded hole in the workpiece to the proper depth, and then manually locked in the workpiece by placing the lock ring on the top of the serrated bourrelet and hammering it into the peripheral lip of the bore. This is a suitable installation technique only when there are a few inserts to be installed in a nonproduction-type assembly or repair project. For most production work, installation tools are the only economically feasible method of installing the stud/inserts because of the time and fatigue factor in the manual technique.
The prior art installation requires the use of two power driven tools. The first is a rotating tool, similar to a power screwdriver, which engages the serrated bourrelet and screws the insert/stud into the threaded hole in the workpiece. The tool is then removed from the stud/insert and a lock ring is placed on the serrated bourrelet. A second tool is fitted in place on the lock ring and hammers the lock ring into the peripheral rim of the bore.
Although this system has worked well enough in the past, it is subject to several disadvantages. The use of two tools is somewhat inconvenient and slow because one tool must be removed and put down and the second tool picked up and fitted in place which is time consuming in the context of a high production operation. In addition, this operation is somewhat fatiguing to the worker because it requires a good deal of manipulation of these installation tools and the hammering of the lock ring into the workpiece is quite noisy and, depending on the workpiece involved, the use of the lock ring hammering tool may actually require hearing protection. Finally, it is not always possible to get the exact desired depth of the insert with the two-tool system. The stud/insert should be threaded into the hole in the workpiece until the top of the serrated bourrelet is just flush with or within about 0.010" below the top surface of the workpiece. This is a difficult precision to achieve with the prior art tools and requires considerable attention on the part of the operator to attain the exact desired depth of the stud/insert.
There is one tool that has been designed for installation of inserts only. It is the subject of U.S. Pat. No. 3,385,378 and it is a satisfactory tool, but is somewhat complicated and expensive, cannot be used to install studs, and hammers the lock ring into the workpiece.